Sexual intercourse with sister is allowed according to some scholars - Tafsir al-Qurtubi 25:54

Quran 25:54 It is He Who has created man from water: then has He established relationships of lineage and marriage: for thy Lord has power (over all things). وَهُوَ ٱلَّذِى خَلَقَ مِنَ ٱلْمَآءِ بَشَرًا فَجَعَلَهُۥ نَسَبًا وَصِهْرًا ۗ وَكَانَ رَبُّكَ قَدِيرًا Ibn Al-Arabi said, "Lineage is an expr...

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